Roll stand for hot-rolling or cold-rolling metallic strips

ABSTRACT

The invention relates to a roll stand for hot-rolling or cold-rolling metallic strips. Said roll stand comprises back-up rolls and work rolls ( 2,3; 4,5 ) which are respectively positioned in chocks ( 6; 7 ) in a rotating manner. Each chock ( 6; 7 ) can be displaced on two sides in guiding devices ( 8 ) of the column frame ( 9 ) for adjusting the roll gap ( 10 ) and can be additionally displaced on at least one side for adjusting the play, by means of horizontal piston cylinder units ( 11 ) arranged in the column frame ( 9 ). The aim of the invention is to completely eliminate the play in the vertical guiding device ( 8 ) of the work roll chocks ( 6; 7 ) during the rolling. To this end, the chocks which are guided on at least one side of the column ( 9   a ) by means of the piston cylinder unit ( 11 ) arranged in the column frame ( 9 ) and by means of one respective support element ( 14 ) which is arranged on the front side of the piston ( 11   a ), can be pressed against the other side of the column ( 9   b ) and the guiding device ( 8 ) thereof without play when the vertical roll positioning drive is stopped, and can be released when the vertical roll positioning drive is switched on.

[0001] The invention concerns a rolling stand for hot rolling or coldrolling of metallic strip material, e.g., of different grades of steel,with backup rolls and work rolls, each of which is pivoted in chocks.Each chock can be displaced on two sides in guiding devices of thecolumn frame for adjusting the roll gap and can be additionallydisplaced on at least one side for adjusting the play by means ofhorizontal piston-cylinder units arranged in the column frames.

[0002] The work rolls of strip trains are exchanged for new work rollsevery 4-6 hours due to wear. The procedure of work roll changing ispresently carried out in an automatic cycle by means of a changingdevice. A gap of a few millimeters is provided between the column andchock to allow free play of the chocks during the vertical displacementfor roll gap control.

[0003] In the hot rolling of individual slabs in a hot strip rollingmill, large impacts with enormous accelerations occur during the initialpass operation. The chocks are thrown against the column guide, which isgreatly stressed. The impact load wears the guideway very quickly, theguide play increases, and the acceleration forces become greater andgreater. Attempts have already been made to reduce these problems withhardened guide rails and a soft, yielding steel.

[0004] In cold rolling, an effort is made to position the work rolls afew millimeters (about 4 to 10 mm) in front of the center of the rollingstand, as seen from the rolling direction, for stabilization. A designthat would be especially favorable would be one in which the mismatch insize could be adjusted, in order to support the profile control.However, the adjustment of the wedge strips at the beginning of therolling operation is also disadvantageous, even if the adjustment isrepeated at intervals of time, because, in light of the demand fordisplaceability of the work rolls, the play cannot be completelyeliminated. On the other hand, this play is necessary, because, duringthe hot rolling operation, the chock heats and expands, but the rollingstand remains cold. To be sure, this reduces the play. However, thisreduction in the play after heating can then again lead to jamming ofthe vertical displacement.

[0005] In all cases, an inexactly defined position of the work rollchocks in the stand is disadvantageous both in cold rolling and hotrolling. In addition, there is the requirement that the chocks must bevertically movable in the column guide. In this regard, it must beconsidered that modern rolling mills operate with so-called automaticgage control (AGC). On the basis of this AGC, a measurement is madeshortly after the initial pass to determine whether the roll gap is ofthe desired size. In case of deviations, a readjustment is made by meansof the hydraulic adjustment equipment in the stand under rolling force.In general, AGC ensures that the metal strip (steel strip) is alwaysrolled With exactly the same thickness, independently of fluctuations intemperature and variations in deforming force. For rolling with aconstant profile of the metal strip, a guide gap between the chock andthe stand column is very unfavorable, because, due to the randomposition of the work rolls in the stand, an undesired offset of the workrolls among themselves can occur, which distorts the desired profile.

[0006] DE 44 34 797 A1 describes equipment for position correction ofthe bearing chocks of the rolls guided in the column windows of rollingstands. This equipment consists of hydraulically operated cylinder pushrods, which are supported in cylinder recesses, which are supported inthe bearing chocks. The cylinder push rods can be moved against one orboth of the guide surfaces of the column windows of the rolling stand.In this way, the guide play of the chocks can be adapted to theparticular course of the rolling process, but it cannot be completelyeliminated. In addition, the detachment and reconnection of thehydrualic connection during roll changes is time-consuming and involvesconsiderable expense; the changing program consists of about 80 rollsper finishing train.

[0007] Equipment for controllably influencing the frictional forcesbetween the guide surfaces and bearing surfaces of the bearing chocks ofthe rolls supported in the column windows of rolling stands is alsoknown (DE 199 11 638 A1), in which flat, bearing support plates, whichcan be acted upon by pressure from behind are installed as guidesurfaces, which are movably supported in these perpendicular to theguide surfaces or support surfaces. However, very large guide surfacesare created in this way, and residual play also cannot be eliminated inthis way.

[0008] The object of the invention is to eliminate completely the playof the work roll chocks in their vertical guide during rolling and inthis way to dispense with a hydraulic connection to the chocks.

[0009] In accordance with the invention, this object is achieved in sucha way that the work roll chocks, which are guided on at least one sideof the column by means of the piston-cylinder unit arranged in thecolumn frame and by means of one respective support element, which isarranged on the front end of the piston, can be pressed against theother side of the column and its guiding device without play, when thevertical roll positioning drive is stopped, and can be released, whenthe vertical roll positioning drive is turned on. In this way, the playof the chocks in the guide devices of the column windows is completelyeliminated during rolling, as a result of which the results of thecontrol by the AGC method are supported, and the rolling profile is moreexactly maintained.

[0010] A refinement of the invention provides that each support elementconsists of a round with plastic guide strips embedded in it along itsperiphery, and that the round is supported in the column frame. In thisdesign, the round absorbs transverse forces that act on the column frameand ensures a rigid construction of the play elimination during therolling. During the changing of work rolls, the round can be moved back.

[0011] Another refinement provides that the round is fastened to thepiston rod of the piston-cylinder unit. In this way, the round carriesout all of the movements of the piston rod.

[0012] In addition, delicate movement of the piston can be achieved ifthe piston of the piston-cylinder unit can be acted upon by pressure onboth sides.

[0013] The feeding of pressure medium is designed in such a way that thepiston-cylinder unit can be supplied with pressure medium throughchannels in the column frame. Thus, during a roll change, it is notnecessary to disconnect and reconnect hose lines.

[0014] In regard to the supplying of pressure medium, it is alsoadvantageous for the channels for the pressure medium to open intogrooves that run around the cylinder of the piston-cylinder unit.

[0015] Furthermore, in a design that is advantageous for the movementsof the round, the round is made of red brass, and the guide stripsembedded in the periphery of the round are made of Teflon.

[0016] The course of the play elimination and the allowance of motionplay during adjustment of the roll gap, i.e., during the verticaldisplacement of the chocks, can be advantageously influenced, if thehydraulic pressure in the piston-cylinder unit can be regulated todifferent pressures for play adjustment or play elimination for thechock in the guiding device of the given side of the column, and if, fora vertical displacement of the chocks, the control can be switched tosignals from an automatic gage control (AGC). In this way, the round canbe pressed axially with full hydraulic pressure against the chock duringthe initial pass, and any play can be eliminated in this way. Duringoperation under AGC, the hydraulic pressure is slightly reduced, so thatvertical displacement of the chocks with the work rolls is madepossible. Therefore, a control which in turn receives the signals of theAGC is advantageous. The control for the round recognizes the time atwhich the AGC requires a vertical displacement of the chock and canreduce the hydraulic pressure in the horizontal piston-cylinder unit ina suitably short time.

[0017] In accordance with additional features, a standard member forprofile control by work roll bending can also be used in a completelyunhindered manner. To this end, it is proposed that, in connection witha bending cylinder that acts on a roll neck and runs perpendicularly tothe roll axis, several individual piston-cylinder units, which arearranged at some distance from the bending cylinder, act on a pistonhead, which is provided with the round. In this regard, it is possibleto use, for example, a May West bending block. A CVC control by axialdisplacement of profiled rolls can likewise be used.

[0018] When bending devices of this type are used, it may beadvantageous if the piston-cylinder units for the round are arrangedsymmetrically to the axis of the bending cylinder in polygonal corners.This arrangement utilizes the available space and the, available surfaceareas around the bending cylinder.

[0019] Furthermore, it may be advantageous, for reasons of area orspace, if the central longitudinal axis of the round is arrangedeccentrically with respect to the axis of the work roll.

[0020] In another variation of the arrangement of several smallerpiston-cylinder units, two or more rounds, each with a smaller circulararea, are provided on the theoretically provided circular area of theround. Measures of this sort may offer design advantages in individualcases.

[0021] In the case that considerable frictional resistance arises, e.g.,static friction, during the change from pressing to release of theround, the invention may also be designed in such a way that the supportelement consists of a sliding shoe, which is shaped similarly to a sledrunner with suitable runner width and engages with the guiding device ofthe chocks.

[0022] The drawings illustrate embodiments of the invention, which areexplained in greater detail below.

[0023]FIG. 1 shows a vertical section through a four-high rolling standin a front view.

[0024]FIG. 2 shows a corresponding side view with a partial sectionthrough the four-high rolling stand.

[0025]FIG. 3 shows an enlarged section through the round with ahorizontal piston-cylinder unit.

[0026]FIG. 4 shows a side view towards the round.

[0027]FIG. 5 shows an embodiment with a bending block on a roll neck andseveral piston-cylinder units for eliminating the play.

[0028]FIG. 6 shows a horizontal section through an embodiment with abending cylinder and several smaller piston-cylinder units foreliminating the play of the chocks.

[0029]FIG. 7 shows a side view towards the round in FIG. 6.

[0030]FIG. 8A shows a side view of an embodiment with twopiston-cylinder units and four guide rods that engage the round.

[0031]FIG. 8B shows a cross section through the arrangement in FIG. 8A.

[0032] The rolling stand in FIG. 1, a four-high rolling stand, is usedfor the hot rolling or cold rolling of metallic strip material 1, whichconsists, e.g., of various grades of steel, and has backup rolls 2, 3and work rolls 4, 5, each of which is pivoted in chocks 6, 7. The chocks6, 7 for the backup rolls 2, 3 or for the work rolls 4, 5 are slidablysupported on both sides in guiding devices 8 of a column frame 9 foradjusting the roll gap 10. In addition, horizontal piston-cylinder units11 are provided on at least one side in the column frame 9 (cf. FIG. 2)for play adjustment of the chocks 6, 7 for the work rolls 4, 5.

[0033] The upper backup roll 2 is equipped with hydraulic operatingcylinders 12, which operate according to an AGC. The lower chocks 7 reston load cells 13 in the column frame 9. The work roll chocks 6, 7 for atleast one column side 9 a are guided in all directions by means of thehorizontal piston-cylinder units 11 arranged in the column frame 9 andby means of a support element 14 arranged on the front end of the piston11 a of each chock, pressed against the other side of the column 9 b andits guiding device without play, when the vertical roll positioningdrive, which consists of the hydraulic vertical operating cylinders 12,is stopped, and slightly released, when the vertical roll positioningdrive is turned on, so that a sliding displacement of the chocks 6, 7can take place.

[0034] Each of the support elements 14 consists of a cylindrical body,which is referred to as a round for short (FIG. 3), such that the round14 a is produced from metal, e.g., red brass, and, on the periphery 14b, guide strips 15 made of plastic, e.g., Teflon, are embedded.

[0035] The round 14 a is fastened to a piston rod 16 of the horizontalpiston-cylinder unit 11 by a screw connection 17. As the drawing shows,the piston 18 of the horizontal piston-cylinder unit 11 can be actedupon by pressure medium on both sides. The pressure medium for thepiston-cylinder unit 11 is fed to the two sides of the piston throughchannels 19 and 20. The channels 19 and 20 run inside the column frame9. The channels 19, 20 open into grooves 22, 23, respectively, that runaround the cylinder 21 and the piston rod 16, respectively. FIG. 4 showsthe circular outer shape of the round 14 a.

[0036] In accordance with an alternative embodiment, the control of thehydraulic pressure in the piston-cylinder unit 11 is adjusted and can besuitably regulated to the different pressures for play adjustment, whenthe vertical roll positioning drive is actuated, or play elimination forthe chock 6 or 7 by actuation of the horizontal piston-cylinder unit 11in the guiding device 8 and the given column side 9 a or 9 b, for which,in a vertical displacement of the chocks 6 or 7 with the backup rolls 2or 3, the control is switched to signals from an automatic gage control.

[0037] Another embodiment (FIG. 5) provides for a connection with abending cylinder 25 that acts on a roll neck 4 a or 5 a and runsperpendicularly to the roll axis 24. In this embodiment, the round 14 aof the support element 14 is formed in the piston-cylinder unit 11,which consists of several smaller piston-cylinder units 27, which arearranged at a distance 26 (cf. FIG. 6) from the bending cylinder 25. Thepiston head 11 b is provided with the round 14 a. The relatively largepiston head 11 b and the relatively small piston-cylinder units 27 aresuitably joined by hexagonal socket screws 33 in order also to be ableto withdraw the given piston head.

[0038] The smaller piston-cylinder units 27 for the round 14 a arearranged symmetrically with respect to the axis 25 a of the bendingcylinder 25 in polygonal corners 28 (FIG. 7).

[0039] In this regard, the central longitudinal axis 29 of the round 14a is arranged eccentrically with respect to the work roll axis 30.

[0040]FIGS. 8A and 8B show another variation of the design, with which,at some distance from the bending cylinder 25, two symmetricallyarranged horizontal piston-cylinder units 11 are supported, each withpaired guide rods 32, which are arranged axially and parallel on thepiston 18 by straps 31 and jointly hold the round 14 a.

List of Reference Numbers

[0041]1 strip material

[0042]2 backup roll

[0043]3 backup roll

[0044]4 work roll

[0045]4 a roll neck

[0046]5 work roll

[0047]5 a roll neck

[0048]6 chock

[0049]7 chock

[0050]8 guiding device

[0051]9 column frame

[0052]9 a side of column

[0053]9 b side of column

[0054]10 roll gap

[0055]11 horizontal piston-cylinder unit

[0056]11 a front end of piston

[0057]11 b piston head

[0058]12 hydraulic, vertical operating cylinder (vertical rollpositioning drive)

[0059]13 load cell

[0060]14 support element

[0061]14 a round

[0062]14 b periphery of the round

[0063]15 guide strips

[0064]16 piston rod

[0065]17 screw connection

[0066]18 piston

[0067]19 pressure medium channel

[0068]20 pressure medium channel

[0069]21 cylinder

[0070]22 grooves

[0071]23 grooves

[0072]24 roll axis

[0073]25 bending cylinder

[0074]25 a axis of the bending cylinder

[0075]26 distance

[0076]27 several smaller piston-cylinder units

[0077]28 polygonal corners

[0078]29 central longitudinal axis of the round

[0079]30 work roll axis

[0080]31 strap

[0081]32 paired guide rods

[0082]33 hexagonal socket screws

1. Rolling stand for the hot rolling or cold rolling of metallic stripmaterial, e.g., of various grades of steel, with backup rolls and workrolls, each of which is pivoted in chocks, such that each chock can bedisplaced on two sides in guiding devices of the column frame foradjusting the roll gap and can be additionally displaced on at least oneside for adjusting the play by means of horizontal piston-cylinder unitsarranged in the column frames, characterized by the fact that the workroll chocks (6; 7), which are guided on at least one side of the column(9 a) by means of the piston-cylinder unit (11) arranged in the columnframe (9) and by means of one respective support element (14), which isarranged on the front end (11 a) of the piston, can be pressed againstthe other side of the column (9 b) and its guiding device (8) withoutplay, when the vertical roll positioning drive is stopped, and can bereleased, when the vertical roll positioning drive is turned on. 2.Rolling stand in accordance with claim 1, characterized by the fact thateach support element (14) consists of a metal round (14 a) with plasticguide strips (15) embedded in it along its periphery (14 b), and thatthe round (14 a) is supported in the column frame (9).
 3. Rolling standin accordance with claim 1 or claim 2, characterized by the fact thatthe round (14 a) is fastened to the piston rod (16) of thepiston-cylinder unit (11).
 4. Rolling stand in accordance with any ofclaims 1 to 3, characterized by the fact that the piston (18) of thepiston-cylinder unit (11) can be acted upon by pressure on both sides.5. Rolling stand in accordance with any of claims 1 to 4, characterizedby the fact that the piston-cylinder unit (11) can be supplied withpressure medium through channels (19; 20) in the column frame (9). 6.Rolling stand in accordance with claim 5, characterized by the fact thatthe channels (19; 20) for the pressure medium open into grooves (22; 23)that run around the cylinder (21) of the piston-cylinder unit (11). 7.Rolling stand in accordance with any of claims 1 to 6, characterized bythe fact that the round (14 a) is made of red brass, and that the guidestrips (15) embedded in the periphery (14 b) of the round are made ofTeflon.
 8. Rolling stand in accordance with any of claims 1 to 7,characterized by the fact that the hydraulic pressure in thepiston-cylinder unit (11) can be regulated to different pressures forplay adjustment or play elimination for the chock (6; 7) in the guidingdevice (8) of the given side of the column (9 a; 9 b), and that, for avertical displacement of the chocks (6; 7), the control can be switchedto signals of an automatic gage control (AGC).
 9. Rolling stand inaccordance with any of claims 1 to 8, characterized by the fact that, inconnection with a bending cylinder (25) that acts on a roll neck (4 a; 5a) and runs perpendicularly to the roll axis (24), several individualpiston-cylinder units (27), which are arranged at some distance (26)from the bending cylinder (25), act on a piston head (11 b), which isprovided with the round (14).
 10. Rolling stand in accordance with claim9, characterized by the fact that the piston-cylinder units (27) for theround (14 a) are arranged symmetrically to the axis (25 a) of thebending cylinder (25) in polygonal corners (28).
 11. Rolling stand inaccordance with any of claims 1 to 10, characterized by the fact thatthe central longitudinal axis (29) of the round (14 a) is arrangedeccentrically with respect to the axis (30) of the work roll. 12.Rolling stand in accordance with any of claims 1 to 11, characterized bythe fact that two or more rounds, each with a smaller circular area, areprovided on the theoretically provided circular area of the round (14a).
 13. Rolling stand in accordance with claim 1, characterized by thefact that the support element (14) consists of a sliding shoe, which isshaped similarly to a sled runner with suitable runner width and engageswith the guiding device (8) of the chocks (6; 7).